1. Field of the Invention
The present invention relates to a centrifugal pump, and more particularly to a pump which pumps out fluid rotated by a nutating impeller.
2. Description of the Related Art
A centrifugal pump which pumps out fluid rotated by a nutating impeller is disclosed in English Pat. No. 720637 and, German Patent Application Publication No. 3133177.
This pump is developed mainly for pumping fluid which must not be contaminated e.g. blood, and is characterized by having a nutating impeller.
The nutation of the impeller is an excellent suggestion in freeing fluid from inevitable contact with a bearing of a rotative impeller of a conventional pump.
But the pump has the defect of low pump efficiency, caused by fluid being forced to rotate without any restriction in the conical room enclosed by the casing of the pump.
On the other hand, another pump with a nutating impeller is disclosed in French Pat. No. 71.40652, but the pump has a defect not only of low pump efficiency caused by its inlet not being located at the center of the room in which the impeller is accommodated but also of the danger of inverse flow or flow disturbance in the room when the pressure at the outlet becomes large.
Especially during pumping of blood, the inverse flow or the flow disturbance in the pump room is unsatisfactory with regard to safety of and damaging of fluid components e.g. blood corpuscles.